This invention relates generally to testing apparatus, and, in particular, to apparatus used to transmit both electrical and pressure signals from rotating test items.
In order to test such devices as jet turbine rotors in operation one must monitor a multitude of test points. Various parameters such as strain, pressure, and temperature are of concern and these are sensed by the devices that output either electrical or pressure signals. These signals must be removed from the rotating test item so that they can be recorded and monitored.
In the past electrical signals have been removed from the test item by use of a conventional slipring assembly which interconnects rotating wires to stationary wires. Pressure tubes from the test item, on the other hand, are reduced in number for output by the use of a select valve which selects one of the rotating pressure tubes for conversion to a stationary electrical circuit by a transducer. This single pressure tube is connected to a stationary transducer that then converts the pressure in the tube into an electrical pressure signal. In the past, only one type of signal, either electrical or pressure, could be removed from the rotating test item because the slipring assembly and the select valve were not easily connected onto the same test fixture. A further problem encountered was the placement of the air pressure transducer. The transducer, it was found, had to be stationary because of calibratin problems caused by rotation and also the increased temperature experienced when the transducer was mounted on the rotating test fixture.
These drawbacks motivated a search for an appratus wherein both the select valve and the slipring could both be mounted but the transducer could be stationary.